Chapter 01

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MEC551 THERMAL ENGINEERING PREPARED BY: PN. ROSNADIAH BAHSAN FACULTY OF MECHANICAL ENGINEERING UiTM SHAH ALAM 1 CHAPTER 01 THERMODYNAMIC & HEAT TRASNFER ENERGY & SUSTAINABILITY http://www.childrensbiblestudy.com

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Transcript of Chapter 01

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MEC551

THERMAL ENGINEERING

PREPARED BY:

PN. ROSNADIAH BAHSAN

FACULTY OF MECHANICAL ENGINEERING

UiTM SHAH ALAM

1

CHAPTER 01

THERMODYNAMIC & HEAT TRASNFER

ENERGY & SUSTAINABILITY

http://www.childrensbiblestudy.com

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OBJECTIVES:

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The objectives of Chapter 1 are to: Understand how thermodynamics & heat transfer related to each other, Understand the basic mechanisms of heat transfer, Develop an awareness on global warming issues, ozone depleting substances, renewable energy and sustainable energy issues.

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1.1 THERMODYNAMICS

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What is Thermodynamics?

Energy Heat

Conservation of Energy principle

Law of Thermodynamics

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1.1 THERMODYNAMICS

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From the Greek words:

therme (heat) & dynamis (power) – the efforts

to convert heat into power

The science of energy transfer

The study of the effects of work, heat and energy on a system

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1.1 THERMODYNAMICS

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concerned with the amount of total

heat transfer as a system undergoes a

process from one equilibrium state to

another

gives no indication of how long the

process will take

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1.1 CONSERVATION OF ENERGY PRINCIPLE

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1.1 CONSERVATION OF ENERGY PRINCIPLE

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Energy cannot be created or destroyed. It

only can be transform from one form to another

form

Conservation of energy principle: During an interaction,

energy can change from one form to another but the total amount of energy remains constant.

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1.1 ZEROTH LAW OF THERMODYNAMICS

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Zeroth Law of Thermodynamics:

Thermodynamic equilibrium & Temperature

If two bodies are in thermal equilibrium with a

third body, they are also in thermal equilibrium

with each other.

By replacing the third body with a thermometer, the Zeroth law can be

restated as two bodies are in thermal equilibrium

if both have the same temperature reading

even if they are not in contact.

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1.1 ZEROTH LAW OF THERMODYNAMICS

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Zeroth Law of Thermodynamics:

Thermodynamic equilibrium & Temperature

Two bodies reaching thermal equilibrium after being brought

into contact in an isolated enclosure.

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1.1 FIRST LAW OF THERMODYNAMICS

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The first law of thermodynamics: An expression of

the conservation of energy principle.

Mathematical model

Ein – Eout = Δesystem

The first law asserts that energy is a thermodynamic property.

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1.1 SECOND LAW OF THERMODYNAMICS

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It asserts that energy has quality as well as

quantity, and actual processes occur in the

direction of decreasing quality of energy.

Example; “a cup of hot coffee left on a table eventually cools,

but a cup of cool coffee in the same room never get hot by

itself”

The high temperature energy of the coffee is degraded

(transform into less useful form at a lower temperature) once

it is transferred to the surrounding air

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1.1 APPLICATION AREAS

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1.1 APPLICATION AREAS

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1.1 APPLICATION AREAS

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1.1 APPLICATION AREAS

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1.1 APPLICATION AREAS

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What is Heat?

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the form of energy

can be transferred from one system to

another

as a result of a temperature difference

Heat

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What is Heat Transfer ?

the physical process by which heat energy moves from one area to another

the determination of rates of energy

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What is Heat Transfer ?

It occurs when the difference temperature exists in a medium or between media

The transfer of heat is normally from high temperature to a lower temperature object.

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1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER

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Heat can be transferred from place to another place by three PROCESSES or MODES.

i) CONDUCTION

ii) CONVECTION

iii) RADIATION

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Conduction Process

The transfer of energy from the more energetic particle of substance to the adjacent less energetic ones as a result of interactions between the particles.

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Conduction in solids

it is due to the combination of vibrations of the molecules in a lattice and energy transport by free electron

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Conduction in solids

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Conduction in solids

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Conduction in liquids and gases

it is due to the collision and diffusion of the molecules during their random motion

http://www.spaceflight.esa.int/

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Conduction Process

Heat flows from the warmer to the cooler

object until the temperature for both objects are the same

The transfer of heat between two bodies or two parts of the same body through molecules

The heat transfer that will occur across the

medium in solids, liquids and gases and from

one to another

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Convection Process

occur between a solid surface and moving fluid at different temperatures

the combined effects of conduction and fluid motion

change of phase of a fluid also considered to

be convection

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Convection Process

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Convection Process

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Natural/Free Convection

if the fluid motion is caused by buoyancy forces that are induced by density differences due to the variation of temperature in the fluid.

The cooling of boiled egg by convection

Convection Process

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Forced convection

if the fluid is forced to flow over the surface by external means such as a fan,

pump, or the wind.

The cooling of boiled egg by convection

Convection Process

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Convection Process

water.me.vccs.edu/

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Convection Process

npg2.com/krdo/weatherblog/

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Convection Process

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ot.com In Boiling Water

www.grammarpolice.net/ www.sltechgroup.com/blog

CONDENSATION

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Convection Process

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A radiator in the room heats up the room by convection

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Radiation Process

Interacts with matter via either:

Emission: Light is released

Absorption: Light is captured

Transmission: Light is allowed to pass through

Reflection: Light is bounced away

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Radiation Process

The energy emitted by matter in the form of

electromagnetic waves (or photons)

Does not require any intermediate

medium for energy transfer

Take place in a vacuum Heat from the sun reaches us by infrared radiation Absorption of infrared radiation causes temperature rise

the transmission of heat energy by

rays passing from a heat source to an absorbing material.

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Thermal Radiation Process

the form of radiation emitted by bodies because

of their temperature

It is volumetric phenomenon and all solids, liquid and

gases emit, absorb, or transmit radiation to varying

degrees.

It differs from other forms of electromagnetic radiation such as X-rays, gamma rays, microwaves, radio waves, and

television waves that are not related to temperature.

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Thermal Radiation Process

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Thermal Radiation Process

Emission of infrared radiation causes the

temperature of the objects themselves to fall

The rate of heat transfer by radiation is affected by the

following factors:

i) Color and texture of the surface

ii) Surface Temperature

iii) Surface Area

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ACTIVITY 1

MODE 1?

MODE 2????

MODE 3?

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ACTIVITY 2

MODE 1?

MODE 2????

MODE 3?

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APPLICATIONS

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http://www.sfu.ca/~mbahrami/research.html

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APPLICATIONS

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APPLICATIONS

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APPLICATIONS

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1.3 SUSTAINABLE ENERGY MANAGEMENT

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energy sources that will allow the Earth to sustain balanced,

healthy ecosystems and human life

WHAT IS SUSTAINABLE ENERGY

energy that can potentially be kept up well into the future without causing harmful repercussions for future generations

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1.3 SUSTAINABLE ENERGY MANAGEMENT

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TYPES OF ENERGY RESOURCES

Renewable Nonrenewable

can be replenished in a human lifetime

take longer than a human lifetime to replace

Source: www.ncpre.iitb.ac.in

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1.3 SUSTAINABLE ENERGY MANAGEMENT

50 World Energy Consumption

1 Quadrillion BTU = 1015 BTU = 1015 x 1054 Joules

World Energy Scenario

Source: www.ncpre.iitb.ac.in

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1.3 SUSTAINABLE ENERGY MANAGEMENT

51 Electricity Consumption Bar Graph

Source: www.ncpre.iitb.ac.in

World Electricity Scenario

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OZONE-DEPLETING SUBSTANCES

a chemical substance

consisting of some combination of chlorine, fluorine,

or bromine plus carbon, such as chlorofluorocarbons

and hydro chlorofluorocarbons that has been shown to

destroy stratospheric ozone

commonly found in aerosol products, foams, and fire

extinguishers, and are used as refrigerants and in air-

conditioning and cooling equipment

1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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www.epa.gov/ozone/science/process.html

1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.3 Ozone Depleting Substances and Global Warming

Issues

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1.4 Renewable Energy Resources and Technologies.

Sustainable Energy Management

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1.4 Renewable Energy Resources and Technologies.

Sustainable Energy Management

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1.4 Renewable Energy Resources and Technologies.

Sustainable Energy Management

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1.4 Renewable Energy Resources and Technologies.

Sustainable Energy Management

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1.4 Renewable Energy Resources and Technologies.

Sustainable Energy Management

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REFERENCES

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1. Yunus A. Cengel, MEC551 Thermal Engineering, McGraw Hill, 1st

Edition, 2011.

2. Yunus A. Cengel, Introduction to Thermodynamics and Heat

Transfer, McGraw-Hill, 2008.

3. Incropera et.al., Heat and Mass Transfer, John Wiley, 6th Edition,

2007.

4. J.P.Holman, Heat Transfer, McGraw-Hill, 10th Edition,2010.

5. P.K.Nag, Heat Transfer, Tata McGraw-Hill, 2003.

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THANK YOU

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SOLID

LIQUID GAS

MELTING/FUSION

FREEZING

BOILING/EVAPORATION

CONDENSATION

DEPOSITION

SUBLIMATION